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Car Care Advice

What Is The Throttle Position Sensor? (Plus Symptoms, Replacement & Costs)

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The Throttle Position Sensor (TPS sensor) in your car helps ensure the proper working of the throttle valve. It has a major effect on proper air and fuel mixture for burning and can cause poor fuel economy and engine performance. 

But what if it malfunctions?
How do you recognize a bad TPS?

In this article, we’ll understand how the TPS sensor works. We’ll also look at the symptoms of a bad throttle position sensor, what happens if you ignore it, if you can replace it by yourself, and the related costs.  

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Let’s begin.

What Is A Throttle Position Sensor?

The throttle position sensor (also known as the TPS sensor or Throttle Valve Position sensor) is a part of the electronic throttle control system and is connected to the throttle body and monitors your vehicle’s throttle angle.

But what does the throttle do? 
The throttle body in your car is located between the air cleaner and the intake manifold of the engine. It has a butterfly valve (throttle opening) that helps control the engine’s power by regulating the amount of air that enters the engine. 

The throttle body is connected to the gas pedal of your vehicle with a cable wire, which moves the throttle shaft when the gas pedal is depressed. 

The throttle sensor monitors the functioning of the throttle. It’s a potentiometer that provides a variable resistance depending on the throttle valve opening angle. With a wide open throttle valve (WOT), the sensor sends an output voltage (signal voltage) of about 4.5 volts to your car’s ECU.  

When you press the accelerator pedal, the throttle sensor tells the Engine Control Unit (ECU) or the Engine Control Module (ECM) that’s happened, and the Mass Air Flow Sensor detects more air. The ECU then manages the air-fuel ratio and determines the best time to trigger the spark plugs for ignition.

In some cases, the TPS isn’t a potentiometer but applies the Hall Effect instead, which involves magnetic fields that shift as the throttle opens and closes.

Note: If the throttle position sensors send a low voltage signal compared to the minimum reference voltage (4.5 volts) threshold, the Engine Control Unit or Engine Control Module will likely trigger trouble codes P0120, P0121, P0122, P0123, or P0124 and activate the check engine light. 

Your mechanic may have to use an OBD II scan tool to conduct a diagnosis. 

Now, what kinds of signs crop up with a bad TPS sensor?

5 Symptoms Of A Faulty TPS Sensor

Here are five important symptoms of a problematic throttle position sensor:

1. Lack Of Power

When the throttle valve position or throttle angle isn’t reported correctly, more air may enter the fuel mixture than the ECU compensates for — which then produces a lack of power for the engine. 

The opposite can also happen due to malfunctioning a TPS, where your vehicle surges forward when you don’t plan to. 

This leads to overall decreased engine performance and other car issues. 

2. Trouble Accelerating The Car 

Since a faulty throttle position sensor can cause reduced engine power, your car may face some trouble during acceleration. 

The car may experience uneven acceleration, or it won’t accelerate after a certain point. This issue may ultimately affect the engine life and lead to poor fuel economy. 

3. Increased Fuel Consumption

A dirty throttle sensor may send false readings to the ECU and cause your engine to consume more fuel than it should, severely decreasing your car’s fuel efficiency.

This is similar to when debris collects around the throttle opening (the throttle plate or the throttle valve), stopping airflow into the engine, and causing issues with unburned fuel passing through the exhaust system. 

4. Uneven Idle

When the throttle plate operation isn’t reported effectively by the TPS, one of the tell-tale signs is poor or low idling. This includes the engine stalling and coming to a stop, a low idle after starting, or stalling when the accelerator pedal is pressed. 

Dirt collected around the throttle can also contribute to a fluctuating idle speed.

5. Illuminated Check Engine Light

The TPS sensor is primarily responsible for monitoring the throttle plate (which controls the amount of air entering the engine). 

If your car has a loose TPS connector (wire) or the throttle sensor fails to monitor throttle functioning properly, it will affect the engine performance, and the engine will trigger the Check Engine Light in response.

When you experience these symptoms, you may ask if it’s something you can resolve yourself.

Can I Replace My Car’s Throttle Position Sensor On My Own?

You can, but it’s best to leave it to a mechanic unless you have sufficient mechanical knowledge. A throttle position sensor replacement can sometimes require other repairs like fuel tank inspection or replacement, so it can be tricky to DIY. 

Moreover, some cars can have a complicated TPS sensor placement, so it’s best to contact your mechanic if you notice a faulty throttle position sensor. 

And what if you don’t do anything about it?

What Happens If I Don’t Replace My Car’s Bad Throttle Position Sensor?

Using a damaged TPS sensor for extended periods may cause engine wear and other noticeable problems. 

Your car may idle or misfire when stopped. You may also notice that your car accelerates itself, hesitates to accelerate, or come to a halt altogether. You may also face difficulty changing gears and experience other issues with the car’s air conditioning, ignition timing (ignition system), or fuel efficiency.

So, what kind of costs are you looking at to get it fixed?

How Much Does A Throttle Position Sensor Replacement Cost?

Depending on the issue’s seriousness, vehicle model, location, and other factors, a TPS sensor replacement can amount to $250 to $500

Note: These costs may vary depending on your mechanic’s labor charges and the cost of car parts. 

Final Thoughts

Your car’s throttle position sensor may not require frequent replacing, but it plays an important role in the functioning of the engine. So it’s essential to practice regular maintenance and replace the throttle position sensor if necessary. 

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